The present invention relates to a de-interleaving method and apparatus therefor, and particularly to a method for receiving interleaved digital audio data of a D2 MAC mode so as to de-interleave the data into pre-interleaved data. The present application is based on the disclosure of Korean Patent Application No. 92-886 filed Jan. 23, 1992, which disclosure is incorporated herein by reference.
The D2 MAC system developed for television broadcast using a satellite in Europe converts an audio signal into a digital signal and time-division-multiplexes the converted digital signal with a luminance signal and a color difference signal. However, an error is created in a digital audio signal during transmission. Particularly, burst error produced in continuous bit trains of audio signal seriously decreases the error correction capability on the receiving side, compared with a random error independently produced in individual bits. In order to solve such a problem, there has been proposed a method for interleaving and transmitting the digital audio signal of the D2 MAC on the receiving side. Generally, the D2 MAC signal is composed as follows.
One frame consists of 625 lines each of which has 648 bits. Each line is comprised of a 6-bit line sync signal, a 99-bit digital audio signal and a 543-bit analog video signal. The 99-bit digital audio signal substantially contains an audio signal and auxiliary data for processing the audio signal. Since, 751 bits constitute one packet in a digital audio signal to be interleaved, approximately, 8 lines of digital audio signal forms one packet so as to be interleaved. The following TABLE 1 illustrates the interleaving sequence in one packet provided that an audio signal occupies one bit.
TABLE 1 ______________________________________ 1 95 189 283 377 471 565 659 2 96 190 284 378 472 566 660 3 97 191 285 379 473 567 661 4 98 192 286 380 474 568 . 5 99 193 287 381 475 . . 6 100 194 288 382 . . 7 101 195 289 . . . 745 8 102 196 . . . 652 746 9 103 . . . 559 653 747 10 . . . 466 560 654 748 . . . 373 467 561 655 749 . . 280 374 468 562 656 750 . 187 281 375 469 563 657 751 94 188 282 376 470 564 658 ______________________________________
One packet of audio data is arranged in the order of 1, 2, 3, . . . , 93, 94, 95, . . . , 750, 751. The interleaving is carried out by re-arranging the data in the horizontal sequence of TABLE 1. That is, the data is re-arranged in the sequence of 1, 95, 189, . . . , 659, 2, 96, . . . , 564, 658 by 94-bit-interval interleaving.
Though errors occur in audio data which is interleaved so as to be transmitted, if de-interleaving is carried out on the receiving side, corresponding to the transmitting-side interleaving, since the burst error is converted into random error, the error correction capability would be improved. However, until now, there has not been proposed a de-interleaving system in which audio data interleaved basically in units of packets is converted into pre-interleaved audio data, and therefore an improvement of error correction capability cannot be expected.